1. Field of the Invention
The present invention relates to turbidity sensing technology and more particularly, to a turbidity sensor for installation in a household appliance for sensing the turbidity of a fluid in a working chamber in the household appliance during operation of the household appliance without interfering flowing of the fluid in the working chamber.
2. Description of the Related Art
Following fast development of electronic technology, many advanced electrical and electronic household appliances are created to service people, bringing convenience to people, helping people save much labor and time and improving the quality and comfort of people's daily living. Many household appliances, such as washing machines and dishwashers, must be connected to a water source and use with a detergent or cleaning agent during working. During the operation of a household appliance to wash thins, such as clothes or dishes, the turbidity of the working fluid will be increased due to the effect of applied detergent, suspended particles and/or any other impurities. Therefore, clean water must be supplied to the working chamber of the household appliance several times before the turbidity of the washing water (working fluid) in the working chamber drops to a predetermined level. Therefore, regular household cleaning appliances (washing machine, dishwasher) are commonly equipped with a turbidity sensor using light-emitting means and light-receiving means for detecting the turbidity of the washing water (working fluid). Subject to the detection of the turbidity sensor, the household appliance can determine the operating mode. Conventional household appliances have different designs and provide different control modes. During the operation of a household appliance, the machine must be interrupted so that the turbidity sensor can detect the turbidity of the working fluid. After turbidity detection, the machine resumes the washing operation. This sensing method wastes much time.
Referring to FIGS. 10˜12, the prior art discloses a turbidity sensor design entitled “Turbidity sensor with temperature sensing for household appliances” for household appliances, in particular washing machines and dishwashers. According to this design, the turbidity sensor comprises a housing A having first and second housing fingers A1;A2, a first optical element A3 arranged in the first housing finger A1, a second optical element A4 arranged in the second housing finger A2 and a temperature sensor A5 arranged in the second housing finger A2. The first optical element A3 and the second optical element A4 are adapted for sensing of the turbidity of a cleaning medium at least partially surrounding the housing A. The temperature sensor A is adapted for sensing the temperature of the cleaning medium.
In application, the aforesaid prior art design still has drawbacks as follows:    (1) The first optical element A3 and the second optical element A4 are respectively arranged in the first and second housing fingers A1;A2 of the housing A that are kept apart from each other within a short distance. In consequence, the sensing ranges of the first optical element A3 and the second optical element A4 is limited, lowering the turbidity sensing accuracy.    (2) Because the first and second housing fingers A1;A2 of the housing A have different lengths, it is difficult to keep the first optical element A3 and the second optical element A4 in accurate alignment. If the first optical element A3 and the second optical element A4 are not accurately aligned, the sensing accuracy will be affected.    (3) Suspended particles tend to be accumulated in the flow-retarding area around the outer side of the first optical element A3 in the first housing finger A1 and the outer side of the second optical element A4 in the second housing finger A2, affecting the sensing accuracy.    (4) The flowing direction and speed of the washing water will be changed due to performance of the sensing operation. Therefore, the washing water must be stopped when sensing the turbidity. However, suspended particles and impurities may float in the washing water when the washing water is stopped from flowing. The single-spot sensing method of the prior art design is not highly reliable. FIGS. 11 and 12 illustrate a flow velocity data obtained from the aforesaid prior art design through a computational fluid dynamics simulation.
Therefore, it is desirable to provide a turbidity sensor for use in a household appliance for sensing the turbidity of a fluid in a working chamber in the household appliance, which does not interfere with the flowing of the fluid in the working chamber and assures high sensing reliability and accuracy.